High-Frequency Energy–Assisted Vacuum Drying of Fresh<i>Eucalyptus globulus</i>

Hansmann, Christian; Stingl, Robert; Prieto, Oscar Gonzailez; López, Carlos Baso; Resch, H.

doi:10.1080/07373930801946759

Cited by 14 publications

(7 citation statements)

References 16 publications

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“…However, CKD has some drawbacks, such as a long drying cycle, high drying stress, and environmental pollution. Many scholars also use special drying methods to dry eucalypti, such as vacuum drying, microwave drying, freeze-drying, and solar drying [5][6][7][8]. Compared with the mentioned above drying methods, supercritical CO 2 drying (SCD) has the advantages of fast drying rate, environmental protection, and simple operation [9].…”

Section: Introductionmentioning

confidence: 99%

Drying Characteristics of Eucalyptus urophylla × E. grandis with Supercritical CO2

et al. 2020

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Supercritical CO2 (ScCO2) is a drying medium with excellent solubility and mass transfer efficiency. Supercritical CO2 drying (SCD) can remove the water of wood rapidly and prevent a change of microstructure caused by capillary tension in the drying process. In this study, Eucalyptus urophylla × E. grandis specimens with lengths of 50 and 100 mm were dried with ScCO2. Conventional kiln drying (CKD) and oven-drying (OD) were used as control. After 1 h, the drying rate, shrinkage, moisture distribution, drying stress were measured to explore the influence of drying methods and specimen length for drying characteristics during the early drying stage. The results showed that compared with CKD and OD, water removal was the fastest under SCD, and the drying rate was nine times of CKD and one time of OD. The shrinkage of SCD was the lowest among the three drying methods. Moisture distribution of SCD and OD was uneven. The drying stress of SCD was relatively high, the drying stress index of it was almost five times of CKD and three times of OD. Regardless of the drying method, shorter specimens had a shorter drying period but greater drying defects than the long specimens.

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Section: Introductionmentioning

confidence: 99%

Drying Characteristics of Eucalyptus urophylla × E. grandis with Supercritical CO2

et al. 2020

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“…It is predicted, however, that the drying time can be further reduced by reducing the vacuum time. In their study, Hansmann et al (2008) have dried Eucalyptus Globulus, which has a high tendency to crack like oak in drying, at a low pressure (76 mbar) with a high frequency and dried from 58% to 10.3% moisture in 5 days. Considering that the rate of hourly drying (0.39%) they have obtained is higher than the values obtained in this study (0.22%) can be resulted due to working at lower pressures, it can be suggested that drying experiments at lower pressures can be made for oak lumber drying.…”

Section: Discussionmentioning

confidence: 99%

Vacuum Drying of Sessile Oak (Quercus Petraea) with Alternative Heating Methods

Altun¹,

Eroğlu²

2017

Kastamonu Üniversitesi Orman Fakültesi Dergisi

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Aim of study: This study was prepared to determine the optimum drying process as a result of application of different parameters of vacuum drying method which is one of the technical drying methods, and to evaluate drying quality of these methods. Area of study: This study carried out at the Karabuk University in Karabuk, Turkey and the materials was obtained from the Karabük Yenice Forest Management Directorate. Material and Methods: Sessile Oak (Quercus Petraea) lumbers in 80x20x2.5 cm were dried at 2 m sec-1 air velocity using two different vacuum periods of 15 and 30 minutes, 2 different heating methods namely plated and IR (infrared) in the kiln were used. Ambient pressure was set at 300 mbar in vacuum periods and 800 mbar in heating periods. Main results: It was observed that the longest drying time was 242 hours (0.15%/hour) with drying in IR heating in 30 minutes periods and the shortest drying time was 126 hours (0.22%/hour) in IR heating with 15 minutes periods. It has been found that the drying time decreases with the decrease of the waiting time in the vacuum. It has been determined that while the drying methods with 15 minutes plated heating, 15 minutes IR heating and 30 minutes IR heating meet the standard (S) drying quality class requirements, drying made with 30 minutes plated heating has reached to the high quality (Q) drying class. Research highlights: IR heating in vacuum drying of Sessile Oak can be used successfully. Shorter vacuumheating periods leads higher drying rates in vacuum drying. Vacuum drying of lumbers wit IR heating meet the standard (S) drying quality class requirements.

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“…Hansmann et al [9] developed a technique to rapidly dry green Eucalyptus globulus with shorter drying times than conventional drying and with better quality (less cracks) [9]. Others have attempted to combine vacuum drying with different technologies to improve drying time and quality.…”

Section: Vacuum Dryingmentioning

confidence: 99%

A Decade of Improved Lumber Drying Technology

Bond

Espinoza

2016

Curr Forestry Rep

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In this paper, we comprehensively review the relevant literature published from 2005 to 2016, focused on lumber drying and provide a summary of where we feel future research will focus. Drying is a critical part of most wood products manufacturing process, and the methods used and proper control are key to achieving the appropriate production level, quality, and costs. While a combination of drying methods may be used, most lumber is dried in a kiln at some point in the process. The most common commercial kilns can be classified as conventional, high temperature, and vacuum; however, there continues to be some interest in solar and compression drying. While no new drying technologies have been proposed, work has continued on improving the existing methods. Control of the drying process varies with the type of kiln used, the species being dried and the temperatures used in the process; however, it usually involves some type of measurement of the moisture content of the wood being dried. The development of new methods for controlling the drying process focuses on new ways to measure moisture content or moisture content variation, temperature drop across the load, and drying stresses. While wood quality can be defined differently by its various users, for example, industrial or end users, certain aspects of quality remain constant across these groups, such as minimizing warp, checks, and splits, and discoloration, and maintaining or enhancing mechanical properties. New schedules have been proposed to increase drying rate and improve drying quality. Methods to reduce drying defects and improve its quality have focused mainly on mechanical restraint to prevent warp, better understanding of defect formation, and pre-treatments to speed up the drying process or reduce final moisture content variation. Finally, concerns regarding the environmental impacts of wood drying, most importantly the high energy demands and emissions, have increased in importance as concerns about sustainability and health issues become more mainstream.

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High-Frequency Energy–Assisted Vacuum Drying of FreshEucalyptus globulus

Cited by 14 publications

References 16 publications

Drying Characteristics of Eucalyptus urophylla × E. grandis with Supercritical CO2

Drying Characteristics of Eucalyptus urophylla × E. grandis with Supercritical CO2

Vacuum Drying of Sessile Oak (Quercus Petraea) with Alternative Heating Methods

A Decade of Improved Lumber Drying Technology

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